Since the first high-speed railway, Japan New Tokkaido Line, is put into operation on Oct. 1, 1964, high-speed MU has been developed increasingly. After more than 40 years' of continuous development, three high-speed MU technical systems represented by Japan New Tokkaido Line, Germany ICE and France TGV have been basically formed. The MU from each country has respective features according to respective actual demands, and they play a positive role in the development of the word's high-speed railway.
France started to research TGV-PSE since 1976, and it was brought into use in September 1981. In May 1990, TGV-A325 reached a running speed of 515.3 km/h on the Atlantic Line, creating a word record of wheel rail system traveling speed. On Apr. 3, 2007, EMU V150 tested by France reached a trial speed of 574.8 km/h, creating a new record of high-speed railway.
Federal Railways tried to manufacture an ICE intercity fast test vehicle in August 1982. An ICE/V test high-speed EMU, which employed a form of 2 tractors and 3 trailers, was successfully manufactured in 1985, and it reached a trial speed of 317 km/h. In May 1988, ICE/V test train created a speed record of 406.9 km/h in the pathway between Hanoverian and Wuerzburg.
Ministry of Railways of the People's Republic of China purchased high-speed railway vehicle technologies from foreign enterprises such as Bombardier Canada, Kawasaki Heavy Industries, Ltd. Japan, Alstom France and Siemens Germany, etc. and started to develop high-speed trains with a speed of 350 km/h and above by vehicle manufacturing enterprises under China CNR Corporation and China CSR Corporation in a mode of introducing and absorbing overseas advanced technologies since 2004.
As one of the most important devices for vehicle roof line security, the insulator attracts the attention of the operation department and the manufacturing industry of electric locomotives. The fast development of China electric grid accelerates the rapid growth of the composite insulator industry, which brings the Chinese manufacturing technology of silicon rubber composite insulator into a world-leading level.
Generally, the number of composite insulator manufacturing enterprises in China has exceeded 100, but only about 10 of them dominates in the market. In addition, insulator manufacturing enterprises engaging in railway security are even fewer. With the rapid increase of train speed and the wide layout of electrified railways, the operational environment of the locomotive roof insulator is more diversified, and the requirements thereof are stricter. In recent years, insulator flashover and tripping accidents tend to be frequent and serious.
FIG. 1 shows the structure of a locomotive roof composite insulator in the prior art. In such an insulator, although the design of the insulating creepage distance between the shed housing and the shed 12 reaches the standard, i.e., exceeding 1000 mm, the arrangement of the shed goes against impulse voltage tolerance. For composite insulating support insulators, the support body 11 and the shed housing interface are bottle necks for insulation. In this case, the insulation voltage possibly tolerated by these parts should be lowered as much as possible in design, and the longitudinal electric field of the interface should be decreased. Therefore, the existing design needs to be properly modified.
In view of the above problems, there is a need for providing an interface breakdown-proof locomotive roof composite insulator so as to solve the problems of the prior art that the arrangement of the shed goes against impulse voltage tolerance and it tends to cause interface breakdown.